SOLUTION - I kept getting the 'Please Check your Driving Wheel" malfunction and the vacuum appeared to be spinning on one wheel so it looked like one wheel wasn't working. Checked for obstructions - there were none. Tested the wheels by manually turning them backward and forward and one appeared to be more free than the other but it was the wheel that was turning easier which was not moving when I pressed the power button. I assumed this difference between the tension of the wheels must have meant one of them was broken BUT IT WASN'T. My ecovacs (T8 but they all appear to be largely the same build) was nearly a year out of warranty so the options were either to pay to get it fixed, throw it out, or see if I could fix it. I tried option 3 and it worked. I took the base cover off (easily removed 8 screws, then unscrewd the two screws which hold the silver housing to keep the battery in place. Unplugged the rechargeable battery (simply pull up) and then reconnected the pins. And it's back to working!